S/O hates baby talk?

My S/O hates when I use baby talk. I try not to do it, but I’ve been working with very young kids so long as a teacher, that sometimes it slips out(ex. Using the word blankie instead blanket).

Yesterday we were kissing and he pulled back and just stopped I could see something was wrong and thought it was my breath(hadn’t brushed my teeth yet) so I apologized and said I’d go brush my teeth. That’s when he tells me he hates the baby/kid talk. I honestly have no idea when it happened/what I said. I explained that I don’t mean it and sometimes it just happens but I feel really hurt whenever he brings it up.